Income Taxes Schedule of Deferred Tax Assets and Liabilities (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]
Deferred Tax Assets, Valuation Allowance		$ 7,200,000
Valuation Allowance, Deferred Tax Asset, Change in Amount	3,900,000
Components of Deferred Tax Assets [Abstract]
Net operating loss		134,418,000	110,989,000
Pension		0	26,452,000
Regulatory liabilities related to income taxes		83,838,000	53,439,000
Other		144,126,000	129,801,000
Total deferred tax assets		362,382,000	320,681,000
Components of Deferred Tax Liabilities [Abstract]
Depreciation and plant related		(814,671,000)	(759,587,000)
Investment tax credit		(25,855,000)	(14,242,000)
Regulatory assets related to income taxes		(66,352,000)	(59,471,000)
Stranded costs		(22,262,000)	(24,934,000)
Deferred Tax Liabilities, Compensation and Benefits, Pensions		(58,780,000)	0
Other		(143,044,000)	(178,492,000)
Total deferred tax liabilities		(1,130,964,000)	(1,036,726,000)
Deferred Tax Assets (Liabilities), Net [Abstract]
Net accumulated deferred income tax liabilities		(768,582,000)	(716,045,000)
Current accumulated deferred income tax (asset) liability		(58,681,000)	258,000
Non-current accumulated deferred income tax liability		(827,263,000)	(715,787,000)
Public Service Company of New Mexico [Member]
Components of Deferred Tax Assets [Abstract]
Net operating loss		99,247,000	93,980,000
Pension		0	32,532,000
Regulatory liabilities related to income taxes		78,849,000	48,027,000
Other		67,179,000	55,629,000
Total deferred tax assets		245,275,000	230,168,000
Components of Deferred Tax Liabilities [Abstract]
Depreciation and plant related		(661,239,000)	(624,724,000)
Investment tax credit		(25,855,000)	(14,242,000)
Regulatory assets related to income taxes		(55,844,000)	(48,726,000)
Deferred Tax Liabilities, Compensation and Benefits, Pensions		(52,104,000)	0
Other		(83,500,000)	(134,046,000)
Total deferred tax liabilities		(878,542,000)	(821,738,000)
Deferred Tax Assets (Liabilities), Net [Abstract]
Net accumulated deferred income tax liabilities		(633,267,000)	(591,570,000)
Current accumulated deferred income tax (asset) liability		(43,827,000)	3,447,000
Non-current accumulated deferred income tax liability		(677,094,000)	(588,123,000)
Texas-New Mexico Power Company [Member]
Components of Deferred Tax Assets [Abstract]
Regulatory liabilities related to income taxes		4,988,000	5,412,000
Other		23,479,000	16,702,000
Total deferred tax assets		28,467,000	22,114,000
Components of Deferred Tax Liabilities [Abstract]
Depreciation and plant related		(151,581,000)	(133,686,000)
Regulatory assets related to income taxes		(10,509,000)	(10,745,000)
Deferred Tax Liability, Loss on reacquired debt		(13,516,000)	(599,000)
Stranded costs		(22,262,000)	(24,934,000)
Other		(14,295,000)	(14,729,000)
Total deferred tax liabilities		(212,163,000)	(184,693,000)
Deferred Tax Assets (Liabilities), Net [Abstract]
Net accumulated deferred income tax liabilities		(183,696,000)	(162,579,000)
Current accumulated deferred income tax (asset) liability		(6,501,000)	(1,131,000)
Non-current accumulated deferred income tax liability		$ (190,197,000)	$ (163,710,000)